As in a conventional frequencymeter or phasemeter, it serves to reconstitute respectively the frequency or the phase of the signal to be evaluated, and to provide an indication of the accuracy with which these parameters are measured together with items for determining the quality of the signal (e.g. signal/noise ratio, form factor).
The signal analysis methods commonly used for measuring frequency and phase are generally based either:
on analog processing and filtering methods for performing interation or counting zero crossing, with the duration of the integration or the filtering being a function of the desired accuracy or: PA1 on methods for locking an oscillator, for example by means of a phase lock loop, thereby isolating the signal to be measured so that measurements can then be performed thereon; or else; PA1 directly on the signal from the locked oscillator, or on the control signals thereof. PA1 on performance, since this technique cannot provide the best possible adaptation to variability in the parameters, and as a result it is more sensitive to disturbing signals (noise, interfering spectrum lines) superposed on the signals to be measured; and also PA1 on complexity, since when using the above-described techniques, it is very difficult to provide optimum adaptation at each of the stages that need to be implemented in order to achieve the desired aim. In particular, the stages of acquisition and of tracking require different characteristics, so they either separate devices, or else they require the characteristics of a set of analog circuits to be adapted to each of these stages, and thus without excessive complication, it is very difficult for the measuring device to be optimally adapted and give best results for each of these stages. PA1 a stage during which numbers corresponding to the samples of the signal to be analyzed are processed in order to convert them into the form of an analytic signal whose real portion coincides with said signal to be analyzed; and, in parallel therewith: PA1 a stage of estimating the parameters to be analyzed which is performed in an overall manner on the basis of estimators and of selection criteria by working on the phase of the signal without using any operator of the fourier transform type or any hypothesis test either separately or simultaneously; and PA1 a stage of estimating the differences between the real signal as taken in this way and the signal obtained from the estimated parameters, thereby making it possible to deliver data in digital form relating to the quality of the analyzed signal and to the reliability of the estimated values. PA1 to determine the precise instants at which the message begins, thereby making it possible subsequently to extract its characteristics; or else PA1 if the message has characteristics which are accurately known, and arrives at random instants in time, to determine the beginning-of-message instants. PA1 a common memory circuit; PA1 a circuit for generating the analytic signal; PA1 a circuit for calculating samples of the phase of the analytic signal and for constructing the developed phase; PA1 a circuit for determining the quality of the signal and enabling an estimate to be made of the statistics of the differences from the estimated sinewave and the estimated noise as a function of the form of the signal to be analyzed; PA1 a circuit for estimating frequency; PA1 with all of the above circuits being connected via respective both-way links to an interconnection bus; PA1 an input circuit for acquiring digitized samples, said circuit being connected to the common memory via a one-way link; and PA1 a coupler having its inputs connected to the outputs from the circuit for determining the quality of the signal and from the circuit for estimating its frequency, and whose output constitutes the output from said processor member. PA1 a second circuit for acquiring digital samples of the phase reference signal and connected like the first sample acquisition circuit to the common memory circuit; and PA1 a circuit for estimating the phase relative to the reference signal, and for estimating the jitter.
The use of these methods suffers from the drawback of not storing the results of earlier processing. As a result, any parameter value estimated from one portion of the signal, is actually made use of in processing a different portion of the signal subsequent to the portion which was used for obtaining the initial estimate, and this has unfortunate consequences both:
Further when performing successive estimates of the same parameter, it is not possible to use the same signal. The results of successive estimates are thus performed over signal periods taken successively in time, which makes it essential to use hypotheses which are guaranteed to provide valid and reproducible results.
The object of the present invention is to mitigate these drawbacks.